In recent years, in a multicarrier mobile communication system, a system for accessing a large volume of data at a high speed has been developed. In addition, in the multicarrier mobile communication system, a low delay is also required. If these demands are met, it becomes possible to realize various applications that require real time property and this increases the possibility that various services can be developed.
The multicarrier mobile communication system is provided with a transmitting apparatus and a receiving apparatus that are connected to a radio network. For example, the transmitting apparatus is used as a base station apparatus that is placed in a base station, and the receiving apparatus is used as a mobile terminal that is utilized by a user. A Hybrid Automatic Repeat Request (HARQ) method is applied to the transmitting apparatus and the receiving apparatus. According to the HARQ method, at first, adding a Cyclic Redundancy Check (CRC) bit to a transmission signal in advance, the transmitting apparatus transmits the transmission signal. The reception signal receives this transmission signal as a reception signal. By using the CRC bit that has been added to the reception signal, the receiving apparatus carries out a retransmission request for the transmission signal when the reception signal has an error.
However, in the multicarrier mobile communication system, a retransmission efficiency is not good while a low delay is requested. One reason for this is in that a scheduling upon retransmission of the transmission signal is made in a constant iteration pattern. In other words, a retransmission request for the transmission signal is carried out on the basis of a CRC execution result. In this case, retransmission occurs in units of addition of the CRC bit (a CRC additional unit) to the transmission signal each time. For example, when the CRC bit is added in units of code word of the transmission signal, retransmission of the transmission signal occurs in the same size each time regardless of the rate at which errors are included in the code word. Accordingly, the retransmission efficiency is not good when the rate that the errors are included in the code word is low.
In conjunction with the above description, technique related to the mobile communication will be described below.
In Japanese Patent Application Publication (JP 2006-211017A), a base station apparatus, a communication terminal, and a resource allocation method are disclosed, which are used for a radio communication system. Comparing MCS levels requested from respective communication terminals during communication, a communication terminal being a data transmission destination is allocated in the resource allocation method. Next, a modulation system and a coding rate of the data to be transmitted to the allocated communication terminal are determined on the basis of the MCS level requested from the allocated communication terminal, an error detecting process result in the allocated communication terminal, and the number of times of iteration of an error correction decoding process that has been carried out in the allocated communication terminal.
In Japanese Patent Application Publication (JP 2007-006382A), a receiving apparatus is disclosed. The receiving apparatus receives a frame including a code block. Next, the receiving apparatus determines a maximum number of times of iteration of each code block on the basis of the size of the code block within the receiving frame and an allowable time about the error correction decoding process of the entire receiving frame. Then, the receiving apparatus iteratively executes the error correction decoding process on each code block with the determined maximum number of times of iteration as an upper limit.
In Japanese Patent Application Publication (JP 2007-043681A), a communication system is disclosed. The communication system communicates with other station via a base station that is connected to a network. The base station divides a packet to be transmitted into a plurality of radio transfer blocks. Then, a priority is determined on the basis of an integration value for the size of each radio transfer block of which delivery confirmation is obtained, and radio resources are assigned to the radio transfer blocks of the packet to be transmitted on the basis of the determined priority. Then, the assigned radio resources are used to transmit the radio transfer blocks. In the mobile station, when the radio transfer blocks are normally received from the base station, a delivery confirmation is transmitted to the base station. When the radio transfer blocks are not normally received from the base station, a retransmission request is transmitted to the base station. Then, a packet is reproduced from radio transfer blocks that are received from the base station.
In Japanese Patent Application Publication (JP 2000-101453A), a decoding apparatus is disclosed. The decoding apparatus serves to decode a plurality of coded messages each having an associated corruption level. The decoding apparatus determines a level of corruption of each message and generates data describing a signal processing requirement amount for decoding each message. Then, the decoding apparatus assigns the messages to decoders depending on the data describing the signal processing requirement amount.
In Japanese Patent Application Publication (JP 2006-121244A), a mobile communication system is disclosed. In response to a propagation quality of a downlink channel from a base station to a mobile station, the mobile communication system determines a transmission system of transmission data of this downlink channel. Measuring the propagation quality, the mobile station turbo-decodes the transmission data. Then, in response to the number of times of iteration of the turbo decoding, the mobile station corrects the propagation quality and notifies the correction to the base station.
In Japanese Patent Application Publication (JP 2004-112800A), an adaptive hybrid automatic retransmission request method is disclosed.
In Japanese Patent Application Publication (JP 2005-184809A), a data transmission method using a hybrid automatic repetitive request in a multicarrier system is disclosed.